Abstract/Summary

Relativistic electron precipitation changes the
chemistry of the upper atmosphere and depletes ozone,
but the spatial and temporal distributions are poorly known.
Here we survey more than 9 years of data from low altitude
satellites for different phases of geomagnetic storms. We
find that for the outer radiation belt, electron precipitation
>300 keV peaks during the main phase of storms whereas
that >1 MeV peaks during the recovery phase. Precipitation
>300 keV can occur at all geographic longitudes in both
hemispheres whereas that >1 MeV occurs mainly poleward
of the South Atlantic anomaly (SAA) region. The data
suggest that wave-particle interactions are strong enough to
precipitate >300 keV electrons into the bounce loss cone,
but precipitate >1 MeVelectrons into the drift loss cone. We
find that whistler mode chorus waves alone cannot account
for the higher MeV precipitation flux during the recovery
phase. We suggest that whistler mode chorus waves
accelerate electrons up to MeV energies during the
recovery phase which are then precipitated by EMIC
waves. The effects on atmospheric chemistry due to MeV
electron precipitation are more likely to occur in the
southern hemisphere poleward of the SAA region with a
delay of 1–2 days or more from the peak of the storm.
Citation: Horne, R. B., M. M. Lam, and J. C. Green (2009),
Energetic electron precipitation from the outer radiation belt
during geomagnetic storms, Geophys. Res. Lett., 36, L19104,
doi:10.1029/2009GL040236.